Method of making vacuum tube base pins



1|||||| J \lllllllL w \swwwx Sept. 20, 1932. A. w. MINER METHOD OF MAKING VACUUM TUBE BASE PINS- Filed Jan. 12, 1929 1 i 1 .lillll flllfllfiiiiffllllvllfltiflrln W 1/ r 31n v 5 w z Z 1 a I Z M M lllll l l lH L ll "m 7 /A, 5 7 5 6 6 Z Z w .z z 1 2 a. I z M 1 I a g Mn AII'SON' W. m, OIFWLTEBBURY, CONN nmss GOODS coaronarron. or warn oommcrrcn'r v nc'rrcur, nssrenon. 'ro ran wa'rnanuay asumr, connnc'ncur. A conroaa'rron or mnon OF MAKING VACUUM TUBE BASE 2m Application med January -18, 1988. Serial No. 888,187.

This invention relates to an improved method of 'maln'ng contact pins for vacuum tube bases, and has for an object to rovide a method of makin these ins where y they may be made seamfess of rawn sheet metal or metal tubing instead'of being turned from solid stock on a screw machine as is now commonpractice- It is also an object of the invention to provide a method of making these pins which will produce a pin of maximum strength for the amount 0 material used, and which will produce an indefinite number of pins of the same size and of uniform construc- Iii-tion with a smooth outersurface devoid of any seam and which will have a better surface finish. p v

With the foregoing and other objects in view, I have devisedthe improved method of making these pins as illustrated in the accompanying drawing. In this drawing, Fig. 1 is a section through a vacuum tube base and a pair of pin contacts applied thereto, and showing how the lead wires are secured to the pins.

Fig. 2 is a top plan view of a blank showing the first step in the manufactureof these pins from sheet metal.

Figs. 3 to 8 illustrate thevarious steps in shaping and drawing the blank to bring the blank to the proper size and length for the final operation of forming the flange.

-Fig. 9 is a section through ,dies shown somewhat diagrammatically for forming the flange or head in the open position before the bead is formed.

Fig. 10 is a similar view showing the dies.

closed and the bead formed.

Fig. 11 is a top plan view and longitudinal sections of one form of finished pin of the larger size.

Fig.'; 12 is a top plan and longitudinal section of a slightly different form. of pin used mostly for the smaller size.

Fig. 13- is a partial lon itudinal section and partial side elevation s owing the bead or flange formed at one end thereof.

- Fig. 14 is a longitudinal section of a pin open at both ends. 1 1 Figs. 15 and 16 show the lower open ends automatic screw machine, and as they of pins in section indicating the different shapes WhlCh may be given to these pins,

and

Fig. 17 is a section ofmold shown somewhat diagrammatically indicatin how' my improved pin may ,be mounted in t e vacuum 7 tube bases. a

In the manufacture of vacuum tubes the glass bulb and the inner partsof the vacuum tube are made and assembled and the bulb no sealed. The Wires connected with the inner parts, such as the filament, plate and gud protrude from the small end of the ulb, .which small end is inserted in and secured in a cup shaped base usuall of molded insulated material in which t e contact pins are ..mounted, and these protruding.- wires are soldered to the respectlve pins to provide the electrical contact or connection with the sockets of the radio set. The contact pins aremade and then either molded into the insulating base as it is made, or the base is first mol ed with openin s for the pin and then the pins are assembled in it. After the pins are properly mounted in the base the end of the bulb carrying the projecting wires is inserted and the wires soldered to the proper pins. A common construction of vacuum tube re uires four ins, two large pins and two smal pins, but t ere are vacuum tubes having more pins, a later form having five of the smaller pins.

For a long time the greater partof these pins have been manufactured from solid brass rod stock by turning and drilling in an 5 required flanges for properly anchoring the pins in the base it will be obvious their manufacture required the turning ofl of considerable metal. Also as they required to be drilled longitudinally the walls were not apt to be of uniform thickness as due to inaccuracy of' the machine or wear the longitudinal openin would not be accurately centered. Furt ermore, if the pins were molded-into the base of a vacuum tube at the time the base was molded the inner ends of these pins were left closed to prevent entrance of the molded material into the pins and these ends had to be later drilled for then inserted and staked in the holes. When,

so staked some of the pins were liable not to be rigidly secured, and therefore, were not absolutely 'rigid as they should beln the holes. Some of this type of pins may also have been molded in the bases, but they are not considered safe to use as there is danger of theseam opening up and allowing the composition to be forced into the tube and also producing a poor contact pin. Such a pin also obviously does not ave a smooth uniform outer surface due to the longitudinal seam, and this seam may retain soldering flux or finishing acids which later corrode the metal.

To overcome these various objections, to produce a better pin and also one which may be manufactured and assembled at less cost I have devised a pin which may be drawn from sheet metal or made from metal tubing and have also devised an improved method of making it. This pin may be drawn of seamless sheet metal or metal tubing and may have either a straight or square end, as shown in Fig. 12, or beveled end, as shown in Fig. 15, or rounded, as

shown in Fig. 16, or the open end may be turned in as shown in 11. It has many advantages over the turned pin or. the rolled up sheet metal pin above described. It may be made either closed at one end, as shown in Figs. '11, 12 and 13, or it may be made open at both ends, as shown in Fig. 14, if the user desires to stake the pins in the molded base instead of molding them in.

In making these pins from sheet metal a circular=blank 20 is blanked from sheet metal of the proper thickness. This blank is then drawn in suitable dies to the proper length anddiameter, the various steps in this drawing operation being shown in Figs. 3 to 7 inclusive. After the tube is properly drawn the open flared end 21 may be trimmed off leaving the tube the proper length for forming the bead orflange, the blank being now I as shown in Fig. 8. Or this tubular blank may be formed by cutting off a proper length of metal tubing. It will be understood that Figures 2 to 8 inclusive are of a somewhat smaller scale than Figs. 11 to 16.

In forming the bead or flange 22 on the blank 23 the blank is confined both inside and out by a set of tools or dies with the exception of the portion where the bead is to be formed,

lower die having a socket to receive one end of the tube, which is the closed end if the tube is of a closed type. and the other die 25 has 3 Ion itudinal opening to receive the blank 3. away or recessed about the openings, as shown at 26,.of a size and shape to correspond with the size and shape desired for the bead. A pin 27 is inserted in the open end of the blank 23 to confine it on the inside. 24, 25 and 28 are forced together subjecting the tubular blank to a lengthwise pressure. As theblank is confined except at the cutouts 26 the wall at this point is forced upwardly. In other words the sides of the blank bulge outwardly and are folded and pressed together, as indicated in Figs. 11 and 12, to form a head 22 of uniform thickness about the tube. This bead mav be formed at any point in the length of the tube either inter:

mediate the ends thereof, as shown in Figs. 11, 12 and 14, or it mav be formed at one end, as shown in Fig. 13.

These pins can be molded in the insulating base 29 of the vacuum tube or they may be P staked in if desired. It is preferred, however, to mold them in as this is cheaper and they are more firmlv secured. The molding of the insulating base is done under considerable pressure in suitable dies. indicated somewhat diagrammatically at 30 and 31, Fig. 17. The lower die or member of the mold 31 has suitably located openings 32 to hold the pins in proper position, and it will be obvious that as the molding is done under considerable pressure there is a tendency to force the composition down into the holes in the molds in which the pins are inserted. If this occurs the pins stick in the holes and the molded bases are broken when an attempt is made to remove them from themolds. To

further reduce this tendency the holes 32 for the pins are sometimes connterbored as shown at 33, and the lower edge of the head 22 forced into the recess thus formed. It will, of

e opposed faces of both dies are out Then the dies r course, be understood that in molding the tubes in the bases the closed end 34 is within the mold to prevent the composition being forced into the pins. After the pins are molded in the bases these closed ends may be drilled for the passage of the lead wires 35 which are soldered to the lower ends of the pins, as indicated at 36 and 37, or the closed ends may be pierced in the dies as described a little later. In assembling the base on the glass bulb these wires are inserted in the pins and cut off at the lower ends and then dipped in molten solder. In the smaller pins, indicated at 38, the opening is of sufficiently small diameter to retain the requiredamount PC I of solder by capillary action, while in the larger pins, indicated at 39, this capillary action is not generally sufficient. The lower end of this tube is, therefore, turned inwardly, as shown at 40, to provide a sufficiently small opening so that the solder will be retained.

In molding the bases of these seamless tubes it is possible to mold the base and pierce the closed end of the pin at the same time. In this operation the upper member 41 of the mold may carry pointed pins or plungers 42 arranged in alignment with the contact pins 38 and 39 in the lower member 31. These plungers can be so arranged that as the composition softens under the action of heat in the molding operation the decrease in resistance allows the plungers to suddenly drop and pierce the closed ends 34 of the contact pins. At the same time the tapered pointed ends of the plungers spread out the ends of the pins as shown at 43, Fig. 1, to thus securely anchor the pins in the composition when it hardens. During this action the ends of the plungers prevent the composition flowing into the pins. Also the beads on the pins efl'ectively seal the pin holes in the die block 31 and prevent the composition entering these holes.

These strong seamless pins have a decided advantage over both the turned pins and the rolled up sheet metal pins having a longitudinal seam. The piercing operation as described does away with the necessity of drilling the pins. These seamless pins are stronger than the turned pins or the pin of the longitudinal seam for the same dimensions and thickness. The walls of the seamless pin are of uniform thickness throughout where there might be considerable variation in the turned pin, and the rolled up pin with the longitudinal seam always has the danger of opening up in the molding operation permitting composition to escape or get into the inside of the pin which, of course, would, therefore, interfere with the connection of the lead wires. These seamless pins have "a smooth uniform outer surface and as a whole have abetter finish than either the turned or rolled up pin. In the rolled up pin with the longitudinal scam the seam is always liable to hold some finishing acid or solution or hold some soldering solution which might afterwards cause tarnishing or corroding o the goods, and it can be made at considerab y less cost than the turned pm.

Having thus set forth the nature of my invention, what I claim is:

1. The method of making a contact pin for vacuum tube bases and the like which havin aligned openings to receive said tube, one 0 said sections having a recess in its surface opposed to the other section and surrounding the opening, and then subjecting the tube to lengthwise pressure to cause the unconfined wall of the tube to bulge outwardly into said recess.

2. The method of making a contact pin for vacuum tube bases and the like which comprises cutting a blank from sheet metal, drawing the blank by successive drawing operations to a seamless tube open at one end and closed at the other end, placing the drawn tube in a die comprising two sections movable toward and from each other and having aligned openings to receive the tube, at least one of the sections having in its surface which is opposed to the other section a recess surrounding the opening and the tube therein, and then moving the sections together in a direction longitudinally of the tube and subjecting the tube to sufficient longitudinal pressure to cause the wall at the recess to bul e outwardly into the recess to form a bead.

3. The method of making a contact pin for vacuum tube bases and the like which comprises cutting a blank from sheet metal, drawing the blank by successive drawing operations to a seamless tube open at one end and closed at the other, placing the drawn tube in a die comprising two spaced sections having aligned openings to receive said tube, and then subjecting the tube to lengthwise pressure to cause the unconfined wall of the tube to bulge outwardly between the sections.

4.- The method of making a contact pin for vacuum tube bases and the like which comprises cutting a blank from sheet metal, drawing the blank by successive drawing operations to a seamless tube open at one end and closed at the other end, placing the drawn tube in a die comprising two spaced sections movable toward and from each other and having aligned openings to receive the tube, and then moving one of the sections toward the other in a direction longitudinally of the tube and subjecting the tube 'to sufiicient longitudinal pressure to cause the wall at the space between the sections to bulge outwardly to form a head.

In testimony whereof I aflix my signature.

ANSON W. MINER.

comprises cutting a blank from sheet metal,

drawing the blank by successive drawing operations to a seamless tube open at one end and closed at the other end, placing the drawn tube in a die comprising two sections 

